Self-cleaning filter assembly

ABSTRACT

A liquid intake assembly includes a filter member having a shower ring for removing solids from the outside surface of the filter member. The shower ring has an annular portion surrounding the filter member and a plurality of nozzle members for directing pressurized fluid in streams adjacent to and generally parallel to the outside surface of the filter member. The streams generate currents in the suspension removing the solids from the outside surface of the filter member.

This application is a continuation of application Ser. No. 07/396,046,filed Aug. 21, 1989, abandoned.

FIELD OF THE INVENTION

The present invention relates to a self-cleaning filter assembly for aliquid intake assembly submerged in a suspension. More particularly, thepresent invention provides a self-cleaning filter assembly for removingsolids deposited on the outside surface of the foraminous filter memberby directing a pressurized fluid in streams adjacent to and generallyparallel to the outside surface of the filter member.

BACKGROUND OF THE INVENTION

Filtering systems for separating solids from a liquid in a suspensionbecome clogged by the solids of the suspension deposited on the outsidesurface of its screen over a period of time. The screen must beperiodicly cleaned to remove the solids deposited on the screen.Usually, the screen or the entire filter must be taken out of thesuspension to be cleaned, disrupting the liquid flow through the filterfor a significant time period.

Filtering systems in large power plants, such as for steam turbinegenerators, supply water as coolant for their operation. In a steamturbine generator a large quantity of cooling water is needed for thecondenser. Accordingly, the plants are situated adjacent large bodies ofwater so that cooling water can be easily obtained as needed. However,before such water can be used as a cooling agent, it must first passthrough a filter to prevent any solid particles contained in the waterfrom entering the condensor.

After a short period of time these filters tend to collect solidmaterials, such as wood chips, leaves, grass, fish and other debris ontheir outer exposed surfaces. This large amount of debris rapidly coversthe screen, greatly reducing and even stopping the flow of water throughthe screen and into the intake for the condenser.

Conventional devices for cleaning the filter screens are disclosed inU.S. Pat. Nos. 4,169,792 to Dovel; 4,518,494 to Jackson; and 4,565,631to Bitzer et al. However, these conventional cleaning devices sufferfrom many disadvantages. The devices requiring moving screens ormechanisms are costly to manufacture and to maintain. Some includespecial movable dividers for causing a backflow or require areciprocating rake mechanism to clean the filter screen. It is alsoknown to use an air backwash system which releases compressed air withinthe filter for causing a backwash through the filter screen removingsolids deposited thereon.

SUMMARY OF THE INVENTION

Accordingly, an object of the present invention is to provide aself-cleaning filter assembly submerged in a suspension that directs apressurized fluid in streams adjacent to and generally parallel to theoutside surface of the filter member to generate currents in thesuspension removing the solids from the outside surface of the filtermember.

A further object of the present invention is to provide a self-cleaningfilter assembly that is inexpensive and easy to manufacture.

Another object of the present invention is to provide a self-cleaningfilter assembly that can be installed onto existing filter assemblies.

A still further object of the present invention is to provide a liquidintake assembly submerged in a suspension having a filter member withnozzle members directing pressurized fluid in streams adjacent to andgenerally parallel to the outside surface of the filter member togenerate currents in the suspension removing the solids from the outsidesurface of the filter member.

The foregoing objects are basically obtained by a self-cleaning filterassembly which includes a foraminous filter member, a conduit, andnozzle members. The foraminous filter member is mounted in a suspensionof liquid and solids and has an outside surface and an inside surface.The suspension flows through the filter member separating the solids ofthe suspension from the liquid portion. The solids are deposited on theoutside surface of the filter member. The conduit is located adjacentthe outside surface of the filter member for conveying the pressurizedfluid. The nozzle members are coupled to the conduit for directing thepressurized fluid in streams adjacent to and generally parallel to theoutside surface of the filter member to generate currents in thesuspension removing the solids from the outside surface.

The foregoing objects are further obtained by a liquid intake assemblysubmerged in a suspension of liquid and solids. The liquid intakeassembly includes an inlet pipe, a generally cylindrical foraminousfilter, an annular conduit and nozzle members. The inlet pipe has anintake end surrounded by the filter member. The outside surface of thefilter member is remote from the intake end of the inlet pipe throughwhich the liquid flows and on which the solids are separated anddeposited. The inside surface of the filter member is adjacent theintake end through which filtered liquid of the suspension flows towardsthe intake end. The conduit is positioned adjacent to the outsidesurface of the filter member and surrounds it for conveying pressurizedfluid. The nozzle members are coupled to the conduit for directing thepressurized fluid in streams adjacent to and generally parallel to theoutside surface of the filter member to generate currents in thesuspension removing the solids from the outside surface.

The foregoing objects are also obtained by a method of in situ cleaningsolids deposited on an outside surface of a foraminous filter membercoupled to an inlet pipe and submerged in a suspension of liquid andsolids. The method comprises the steps of conveying pressurized fluidadjacent to the outside surface of the filter member, and directing thepressurized fluid in streams. The streams of pressurized fluid moveadjacent to and generally parallel to the outside surface of the filtermember generating currents in the suspension and removing the solidsfrom the outside surface of the filter member.

By surrounding a filter member with an annular conduit having nozzlemembers generally parallel or angled slightly towards the outsidesurface of the filter member, currents are generated adjacent to theoutside surface by the flow of pressurized fluid from the nozzlemembers. The currents remove deposits on the outside surface.

As used herein, "cylindrical" is not limited to a right circularcylinder, as illustrated, but also includes such shapes asparallelepipeds, elliptical cylinders and cones.

Other objects, advantages and salient features of the invention willbecome apparent from the following detailed description, which, taken inconjunction with the annexed drawings, discloses a preferred embodimentof the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a liquid intake assembly with aself-cleaning filter assembly coupled thereto in accordance with thepresent invention.

FIG. 2 is an end elevational view in section taken along line 2--2 ofFIG. 1.

FIG. 3 is an enlarged partial, cross-sectional view of the shower ringtaken along line 3--3 of FIG. 2 with the filter member in elevation.

DETAILED DESCRIPTION OF THE INVENTION

Referring initially to FIG. 1, a liquid intake assembly 10 in accordancewith the present invention includes an intake well 12, a foraminousfilter member 14 and a shower ring 16. FIGS. 1-3 illustrate liquidintake assembly 10 connected to a power plant, such as a steam turbinegenerator, for providing cooling water to its condenser. When used witha power plant as illustrated, liquid intake assembly 10 is constructedon the shoreline of a large body of water, such as a lake or a largeriver, in a conventional manner. Liquid intake assembly 10 is notlimited to filtering cooling water for a power plant, as illustrated,but can be used for filtering various suspensions of liquid and solidsin other devices.

Intake well 12 includes a concrete wall 18 having a plurality of inlets20 extending therethrough for drawing liquid from the suspension intointake well 12. Since all of the inlets are substantially identical,only one inlet 20 will be shown and described in detail herein.

Inlet 20, as seen in FIG. 1, includes an inlet pipe 22, a valve assembly24, a filter guide rail assembly 26 and a sealing plate 28. Inlet pipe22 extends through concrete wall 18 with valve assembly 24 coupled toits inner end 30 extending into the intake well 12 for opening andclosing the flow of liquid through inlet pipe 22. A sealing plate 28,coupled to outer end 32 of inlet pipe 22, extends out of the intake well12 for engaging filter member 14.

Guide rail assembly 26 is coupled to outer surface 34 of concrete wall18, and includes a pair of parallel rails 36 extending vertically onouter surface 34 of concrete wall 18. The rails are spaced apart forslideably receiving a portion of filter member 14. Each rail 36 isgenerally C-shaped in transverse cross section, and has an upper flaredend 38 and a lower end 40 with a stop member 42 coupled thereto. Stopmember 42 engages filter member 14 to stop its downward movement inrails 36, and aligns filter member 14 with inlet pipe 22.

Filter member 14 includes a guide plate 46, an extension pipe 48, acylindrical screen portion 50, a dish head 52 and an optional airbackwash system 54.

Guide plate 46 is preferably about 72 inches high, about 77 5/8 incheswide and about 1 inch thick, and made of 1/2 inch thick stainless steelplate AISI No. 316L coupled to a 1/2 inch member cf a protectivematerial. The guide plate is slideably received between guide rails 36as seen in FIGS. 1 and 2 for raising and lowering filter member 14 intoand out of the suspension. In its lowermost position as seen in FIG. 1,guide plate 46 abuts against sealing plate 28 to form a sealtherebetween. Four support members 61, 62, 63 and 64 are coupled toguide plate 46 by welding or other suitable methods, and extendperpendicularly from the guide plate for supporting shower ring 16.

Extension pipe 48 is coupled to guide plate 46 by welding or othersuitable methods, and extends substantially perpendicular to guide plate46. Inlet pipe 22 becomes aligned with extension pipe 48 when filtermember 14 is lowered to its lowermost position (i.e., when guide plate46 engages stop members 42).

Screen portion 50 is substantially cylindrical in shape, preferably aright circular cylinder. As illustrated, the diameter of screen portion50 is about six feet in diameter and about six feet in length. Screenportion 50 extends substantially perpendicular to guide plate 46 and iscoupled thereto by welding or other suitable methods. The screen portionis preferably made of stainless steel (AISI No. 316L) and can be madefrom screen material manufactured by Johnson under the trademarkVEE-WIRE screen having 0.125 inch slot openings.

Dish head 52 is releasably coupled to screen portion 50 and closes theend of filter member 14 remote from guide plate 46. Dish head 52 ispreferably made of stainless steel (AISI No. 316L). Three liftingbrackets 60 are coupled to filter member 14. One lifting bracket iscoupled to the uppermost portion of dish head 52, while the remaininglifting brackets are coupled to guide plate 46. Cables can be coupled tolifting brackets 60 for lowering and raising filter member 14 into andout of the suspension.

Air backwash system 54 has a pipe 55 extending through screen portion 50into filter member 14 for blowing compressed air therein. The compressedair passes from inside surface 56 through screen portion 50 to removedebris and other solids deposited on outer surface 58 of screen portion50. Air backwash system 54 is well known in the art, and thus, is notdisclosed in detail herein.

Air backwash systems in filtering systems of power plants, asillustrated, do not remove all of the solids (i.e., river debris)deposited on outer surface 58 of screen portion 50 during periods offull moon (i.e., extreme tidal difference). This period experiencesextreme quantities of river debris with the changing of the tide.

Shower ring 16 includes a conduit 68 with an inlet portion 70 and anannular portion 72, a plurality of nozzle members 74 and four mountingbrackets 76, 77, 78 and 79. Preferably, there are 41 nozzle members 74equally spaced around annular portion 72 of conduit 68. Each nozzlemember is fixedly mounted on conduit portion 72, is in fluidcommunication with the interior of conduit portion 72, and extendsgenerally parallel to the axis of annular portion 72 and to screenportion 50.

In the illustrated embodiment, conduit 68 is preferably made ofstainless steel (AISI No. 316L) with its annular portion 72 made ofabout 4 inch diameter pipe. The diameter of annular portion 72 from thecenter of one nozzle member to the center of the opposite nozzle memberis about 78 inches.

Inlet portion 70 has a first portion 80, a transition portion 82, and asecond portion 84. First portion 80 has a diameter of about 4 incheswhile second portion 84 has a larger diameter equal to the diameter ofthe conduit extending from pressurized fluid supply 86. An annularflange 85 extends from the free end of second portion 84 and is engagedby a moveable coupling ring 86. Ring 86 slideably surrounds inletportion 70 for coupling shower ring 16 to a conduit extending frompressurized fluid supply 86.

Fluid supply 86 can be from the water discharge from the intake pumps orother suitable source such as the fire protection system. In any event,the fluid supply should be capable of delivering a pressure greater than30 psi.

Referring now to FIG. 3, nozzle members 74 are preferably angledslightly towards the adjacent portion of outside surface 58 of screenportion 50 at an angle A. Preferably, angle A is about 2°-30 minutes. Inthe illustrated embodiment, nozzle members 74 are preferably 3/8 inchdiameter nozzles with a 1/4 inch diameter orifice capable of emitting9.3 gallons of water per minute at a velocity of 60.78 feet per secondat the tip of the nozzle members. The streams of current generated inthe suspension by nozzle members 74 should have a velocity of about 1.57feet per second at the end of screen portion 50 adjacent to dish head52.

Shower ring 16 is releasably coupled to guide plate 46 of filter member14. Support arms 61-64 extending perpendicular to guide plate 46 arecoupled to brackets 76-79 by bolts 90 and 92, as seen in FIG. 3.Brackets 76-79 are fixed to annular portion 72 in any suitable manner.

In operation, shower ring 16 is coupled to filter member 14 and thenlowered into the suspension by placing guide plate 46 between rails 36and allowing the filter member to slide down into the suspension. Thedownward movement of filter member 14 is stopped when guide plate 46engages stop members 42, aligning extension pipe 48 with inlet pipe 22.

Water entering intake well 12 via inlet pipe 22 must pass through screenportion 50 of filter member 14. When solids begin to deposit upon screenportion 50 of filter member 14, high pressure fluid is supplied throughconduit 68 to nozzle members 74 for directing the pressurized fluid instreams adjacent to and generally parallel to outside surface 58 offilter member 14. The streams generate currents in the suspension toremove the solid deposits from outside surface 58 of screen portion 50.

While only one embodiment has been chosen to illustrate the invention,it will be understood by those skilled in the art that various changesand modifications can be made therein without departing from the scopeof the invention as defined in the appended claims.

What is claimed is:
 1. A self-cleaning filter assembly, comprising:agenerally cylindrical foraminous filter member having opposed first andsecond longitudinal ends, said filter member being mounted in asuspension of liquid and solids having an outside surface through whichthe suspension flows and on which solids of the suspension are separatedand deposited, and an inside surface through which a filtered liquidportion of the suspension flow; an annular conduit, fixedly locatedadjacent said first end of said filter member and surrounding saidoutside surface, for conveying pressurized fluid; and a plurality ofspaced apart nozzle members coupled to said conduit, for directing thepressurized fluid toward said second end of said filter member instreams adjacent to and generally parallel to said outside surface ofsaid filter member to generate currents in the suspension removing thesolids from said outside surface without the use of brushes.
 2. Aself-cleaning filter according to claim 1 whereineach of said nozzlemembers is angled to about 2.5° towards said outside surface.
 3. Aself-cleaning filter according to claim 1 whereinsaid filter member isgenerally a right circular cylinder.
 4. A self-cleaning filter accordingto claim 1 whereinsaid conduit has a plurality of brackets extendingtherefrom releasably coupling said conduit about said filter member. 5.A liquid intake assembly submerged in a suspension of liquid and solids,comprising:an inlet pipe having an intake end; a generally cylindrical,foraminous filter member having opposed first and second ends, the firstend of the filter member surrounding said intake end of said inlet pipe,said filter member having an outside surface remote from said intake endthrough which the liquid flows and on which the solids are separated anddeposited, and an inside surface adjacent said intake end through whichfiltered liquid of the suspension flows toward said intake end of saidinlet pipe; an annular conduit, fixedly located adjacent said first endof said filter member and surrounding said outside surface, forconveying pressurized fluid; and a plurality of spaced apart nozzlemembers, coupled to said conduit, for directing the pressurized fluid instreams adjacent to and generally parallel to said outside surface ofsaid filter member and away from the first end to generate currents inthe suspension removing the solids from said outside surface without theuse of brushes.
 6. A liquid intake assembly according to claim 5 whereineach of said nozzle members is angled at about 2.5° towards said outsidesurface.
 7. A liquid intake assembly according to claim 5 whereinsaidfilter member is generally a right circular cylinder.
 8. A liquid intakeassembly according to claim 5 whereinsaid conduit has a plurality ofbrackets extending therefrom releasably coupling said conduit to saidfilter member.
 9. A liquid intake assembly according to claim 5whereinthe volume of each of said pressurized streams of fluid issubstantially nine gallons of water a minute at the tip of each of saidnozzle means, and the velocity of each of said pressurized streams offluid is substantially 60 feet per second at the tip of each of saidnozzle means.
 10. A liquid intake assembly according to claim 5 furthercomprisinga dish head mounted at the second end of said foraminousfilter member.
 11. A liquid intake assembly according to claim 5 furthercomprisinga dish head mounted at the second end of said foraminousfilter member, and wherein the velocity of each of said pressurizedstreams of fluid is substantially 60 feet per second at the tip of eachof said nozzle means and the velocity of each of said pressurizedstreams of fluid at said second end of said filter member adjacent saiddish head is substantially 1.5 feet per second.